The sensation of pain is associated with numerous physiological and psychological ailments and is a universal experience of all complex living organisms. Pain, as the mental manifestation of a neurological response, is an important biological attribute and critical to living and adapting to the environment. Notwithstanding this important role, the alleviation of pain has been a fundamental goal of medicine for as long as the medical profession has existed. Indeed, the ability to control the neurological pathways through which pain is conveyed, has made complex procedures far simpler to implement and much less traumatic to the patient.
There is additionally a class of neurological response which is associated with pain that does not correspond to or act as a warning for a particular physical damage or biological dysfunction. In fact, many biologically important transitions are characterized by significant pain, such as the withdrawal period of an addict, during which time the addict's system is depleted of a specific endogenous narcotic. Other mental conditions which are neurological response dependent conditions include depression, hypertension, causalgia pain, insomnia and jet lag.
The importance of the ability to control neurological response and associated perceptions of pain and distress has led to the development of many pain control methodologies. The most common of which employs bio-active chemical agents that act to block neural transmission pathways within the body. These are designed to operate locally for spot treatment or broadly for generalized control or inhibition of pain response throughout the body. Chemical interference with pain signals has broad based appeal, but in many instances is unacceptable. For example, certain chemicals have toxic side affects or cause allergic reactions to certain patients. For more chronic ailments, such as chronic migraine headache syndrome, continuous absorption of chemical narcotics may reduce the associated pain, but at unacceptable high costs associated with interference with routine activities, addiction and/or toxicity of the narcotic.
In view of the problems associated with chemical pain control, efforts have abounded to discover treatment approaches which would not involve pharmacological (chemical) interference with neural transmitters in the body. One approach that has recently sparked tremendous interest is the use of low power electrical stimulator devices capable of passing currents across key neural transmitter junctions in the body and thus effecting a blockage of neurological pathways which are inducing messages of pain to the brain. A practical implementation of this approach is disclosed in U.S. Pat. No. 3,902,502 to Liss, et al; the teachings of which are herein incorporated by reference.
The system disclosed in the '502 patent presented a pulsed direct current waveform having a high frequency carrier modulated by a single low frequency modulation. It was discovered that this waveform was particularly successful at controlling symptoms of certain neurological disorders.
Although effective for its applied treatment, many electrical stimulatory devices are limited to certain applications and lack the requisite flexibility for broad-based appeal. In addition, a drawback to the use of electrical stimulation to control pain is the concern by patients and others about the impact of power dissipation on the patient. Although low current, the power dissipation of many of the electrical stimulation devices is still quite significant. Efforts to reduce the applied power have resulted in stimulation devices with little or no physiological impact.
There has been, therefore, a search for new electrical stimulation devices characterized by exceptional pain management capabilities while reducing the overall patient exposure to electrical energy. The present invention is a result of this search.